The Columbia University Center for Population and Family Health and the Institute for Population and Social Research of Mahidol University, Bangkok, propose to conduct a research project to study patterns of sexual activity and AIDS/STD related knowledge, attitudes and practices, in low income (slum) areas in three cities of Thailand. The project, to be conducted in Bangkok in central Thailand, Chiang Rai in the north, and Hadyai in the south, will collect quantitative and qualitative behavioral data in brothels (included in the study will be brothel owners, and manager, commercial sex workers, and clients); and from patients in STD clinic, long distance truck and bus drivers at their place of work, and low income neighborhood youth contacted at typical social gathering places. IAP data will also be collected from the adult and adolescent male population via random household surveys in the study communities. The three cities have been selected because they are important foci in the domestic and international commercial sex industry. The study populations are themselves potentially at high risk of acquiring HIV, particularly through sexual channels, and may act as sources of infection to wider segments of the Thai population. Contextual, intermediate and proximate determinants of high risk behavior, and their interrelations, will be examined. Methods of modifying such determinants and the resulting effects on behavior will be postulated using the conceptual framework of the AIDS Risk Reduction Model. The project will also be the first in Thailand to investigate migration and travel patterns as a factor in the transmission of HIV infection. Data will be analyzed to indicate networks of social and sexual interactions between the study populations, to project the potential for the transmission of HIV infection between these groups and from them to other segments of the Thai population, and to serve as a basis for developing effective strategies for the prevention of high risk behavior. Selected behavioral interventions which the project proposes to test include peer counseling and condom distribution in the brothels, involvement of brothel owners and managers in safe sex programs for their employees, and AIDS education and condom distribution through trucking companies. In large part, the project's support of interventions will occur through existing implementing agencies in Thailand.